Occupant restraint systems, and particularly inflatable occupant restraint systems, are increasingly being used in automotive vehicles. Nearly every vehicle now produced has driver and passenger front airbags. Side airbags are also increasingly being used in automotive vehicles. Side airbags use lateral acceleration sensors to detect lateral acceleration of a vehicle and thus the presence of a side impact. In response to lateral acceleration, the side airbags are deployed in side impacts.
Another newer type of inflatable occupant restraint system is a side curtain airbag. The side curtain airbag deploys from the ceiling or near the roof header and extends downward in front of the side windows of the vehicle. This system is designed to protect occupants in rollover conditions.
Another type of non-inflatable system is a pretensioner system coupled to a seat belt. A pretensioner system reduces the amount of play (i.e., slack) in seat belts upon a sensed rollover condition.
Each of the above systems may potentially be employed during rollover of a vehicle. Commonly, an energy-based model is used to determine when rollover occurs. However, in a deployment scenario, an energy-based model may not allow enough time for full deployment.
The present invention builds upon U.S. Pat. No. 6,282,474 to the same assignee. Rollover protection systems require a significant amount of testing. The testing requires the use of destructive testing of actual vehicles. During various stages of vehicle development, these tests are performed. Using prototypes for testing requires a significant amount of time and manpower, and the prototype vehicles are very expensive. It would therefore be desirable to provide a rollover sensing algorithm that has less dependence upon testing prototypes so as to reduce overall costs to the system.
It would also be desirable to provide an accurate determination of rollover when deploying the restraints.